<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <script>
        function VerificationCode(){
            var arr = [0,1,2,3,4,5,6,7,8,9,'a','b','c','d', 'e', 'f', 'g', 'h'];
            var str = '';
            for(var i=0;i<6;i++){
                var a = parseInt(Math.random()*arr.length);
                console.log(a);
                str += arr[a];
            }
            return str;
        }
        var s = VerificationCode();
        console.log(s);
    </script>
</body>
</html>